U.S. patent number 6,159,363 [Application Number 09/293,015] was granted by the patent office on 2000-12-12 for water carafe filter cartridge.
This patent grant is currently assigned to Corning Incorporated. Invention is credited to Thomas A. Collins, Willard A. Cutler, David L. Hickman, Alfred N. Mack.
United States Patent |
6,159,363 |
Collins , et al. |
December 12, 2000 |
**Please see images for:
( Certificate of Correction ) ** |
Water carafe filter cartridge
Abstract
A gravity-flow water filter cartridge for use in a drinking
water carafe or the like includes a high-surface area cyst
reduction filter element disposed in a water-retaining reservoir
within the cartridge; the reservoir retains sufficient water
between filtering and during dispensing cycles to maintain the
filter element in a fully immersed state, whereby the primed
(air-free) condition of the filter necessary for fast gravity flow
at high cyst reduction efficiency is maintained.
Inventors: |
Collins; Thomas A. (Horseheads,
NY), Cutler; Willard A. (Big Flats, NY), Hickman; David
L. (Big Flats, NY), Mack; Alfred N. (Corning, NY) |
Assignee: |
Corning Incorporated (Corning,
NY)
|
Family
ID: |
26769647 |
Appl.
No.: |
09/293,015 |
Filed: |
April 16, 1999 |
Current U.S.
Class: |
210/136; 210/248;
210/266; 210/433.1; 210/472; 210/473 |
Current CPC
Class: |
C02F
1/003 (20130101); C02F 1/283 (20130101); C02F
2201/006 (20130101); C02F 2307/04 (20130101) |
Current International
Class: |
C02F
1/00 (20060101); C02F 1/28 (20060101); B01D
035/153 () |
Field of
Search: |
;210/136,266,282,284,464,472,473,474,476,248,433.1,434,97,120,436
;222/189.06,189.08 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
|
|
|
|
|
|
|
2197647 |
|
Mar 1990 |
|
GB |
|
96/31440 |
|
Oct 1996 |
|
WO |
|
Primary Examiner: Drodge; Joseph W.
Attorney, Agent or Firm: Kees van der Sterre
Parent Case Text
This application claims the benefit of U.S. Provisional Application
Ser. No. 60/083,724, filed Apr. 30, 1998, entitled "Water Carafe
Filter Cartridge", by Collins et al.
Claims
We claim:
1. A gravity-flow water filter cartridge comprising:
a water-retaining reservoir; and
a microporous cyst reduction filter element disposed in the
reservoir;
the water-retaining reservoir (i) having a retained water capacity
sufficient to cover the filter element when the cartridge is in an
upright orientation; and (ii) being configured to retain water at a
level sufficient to cover the filter element at cartridge tilt
angles ranging up to 90 degrees away from the upright orientation
in at least one tilting direction.
2. A gravity-flow water filter cartridge in accordance with claim 1
wherein the cartridge includes at least one check valve, and
wherein water drainage from the reservoir is restricted at
cartridge tilt angles of up to 150 degrees away from the upright
orientation.
3. A gravity-flow water filter cartridge in accordance with claim 1
which comprises a drain port or drain conduit having an entry point
at or above the level sufficient to cover the filter element.
4. A gravity-flow water filter cartridge in accordance with claim 1
which comprises a pre-filter positioned upstream of the
high-surface-area cyst reduction filter element.
5. A gravity-flow water filter cartridge in accordance with claim 1
which comprises a gooseneck drain conduit (i) having an entry point
below the level sufficient to cover the filter element, and (ii)
including a length portion extending to a height above said
level.
6. A gravity-flow water filter cartridge in accordance with claim 5
wherein the gooseneck drain conduit includes an anti-siphon air
inlet.
7. A gravity-flow water filter cartridge in accordance with claim 1
which comprises an air bubble chamber opening into the reservoir at
an entry point above the level sufficient to cover the filter
element, the chamber providing a collection space for air bubbles
developed in the reservoir during filling or tipping of the
cartridge.
8. A gravity-flow water filter cartridge in accordance with claim 1
which comprises a water entry tube attached to and extending
outwardly from a water inlet port in the cartridge, the entry tube
having a water entry opening which is disposed above the water
inlet port when the cartridge is tipped.
9. A gravity-flow water filter cartridge for a water carafe
comprising:
a filter housing incorporating one or more water purifying elements
and being adapted for mounting in an upright filtering orientation
within a filter cartridge holder in a water carafe;
a micro-porous water filter element disposed within the housing;
and
water reservoir means for preventing air contact with the
micro-porous filter element when the filter housing is in an
upright position and when the filter housing is in a tipped
orientation for pouring;
the water purifying elements including at least one element
selected from the group consisting of adsorbents and ion-exchange
resins, and
the filter housing comprising a base housing and a housing cover
sealed thereto, the housing cover incorporating a water inlet port
connected to a bypass water conduit and the bypass water conduit
opening into the interior of the base housing at a point below the
position of the micro-porous water filter element disposed
therein.
10. A gravity flow water filter cartridge in accordance with claim
9 wherein the housing cover incorporates an overflow port for the
outflow of treated water from the housing.
11. A gravity flow water filter cartridge in accordance with claim
10 wherein the overflow port is connected to a drain port in the
housing cover, the drain port opening into a drain conduit disposed
within but traversing the housing and having an outlet at the base
of the housing for discharging treated water into a treated water
reservoir disposed beneath the cartridge.
12. A gravity flow water filter cartridge in accordance with claim
9 wherein the housing cover incorporates sealing means for forming
a water-tight seal between the housing and the filter cartridge
holder.
13. A gravity-flow water filter cartridge in accordance with claim
9 which includes an activated carbon adsorbent.
Description
BACKGROUND OF THE INVENTION
Gravity flow carafe filters have been commercially available for
several years and their popularity with consumers continues to
grow. Currently available commercial water carafes are capable of
removing lead using an ion exchange resin, undesirable tastes and
odors using carbon granules, and large particles using a packed bed
configuration. However, up to the present time, water carafes of
commercially available design have not been capable of parasite
reduction, which requires much finer filtration. Nor have they been
effective for the complete removal of organic chemicals, pesticides
and insecticides, which requires more carbon. While such additional
removal attributes are desirable, they have not been technically
feasible in the filter sizes required and at the filter cost
currently in the market.
The need for additional carafe functionality has been recognized
and proposals to add parasite reduction capabilities have been
made. A major problem to be solved for carafe applications,
however, is that of achieving an adequate filter flow rate. Unlike
filter cartridges for in-line or pressurized water filtration
systems, cartridges for carafes must operate under water pressures
developed by gravity alone. Membranes and other micro-porous filter
materials with porosity sufficiently fine to exhibit cyst reduction
capability have for the most part been viewed as exhibiting
inadequate flow rates for systems other than those using a
high-pressure water supply.
SUMMARY OF THE INVENTION
The present invention provides a gravity-flow water carafe filter
with the capability of substantially removing parasites in the cyst
stage, while still maintaining an adequate filter flow and a
reasonable filter size. The invention is based in part on the
discovery that micro-porous filtration materials previously
considered useful only in pressurized water filtration systems
function very effectively in a gravity flow environment, if
properly maintained. In particular, many of the micro-porous filter
materials previously used only in pressurized systems have been
found to exhibit good gravity flow characteristics if maintained in
an adequately primed condition throughout the period of use.
This finding is contrary to experience gained through the study of
more conventional carafe filter designs. In general, the latter
filters will demonstrate acceptable water flow rates once
thoroughly wetted, and as long as they are kept somewhat moist in
use. In fact, the presence of substantial air pockets within the
filter beds of these filters, even during periods of high water
flow, is common and not considered to be detrimental to filter
performance.
In contrast, for micro-porous filter materials capable of cyst
reduction performance we have found that sustaining high
gravity-only flow rates throughout the useful life of the filter
requires maintaining the filter element in a fully primed condition
during the entire period of filter use. The primed condition is a
condition under which substantially all of the air residing in the
pore structure of the porous filter element has been expelled and
replaced with water.
Maintaining a fully primed condition, i.e., preventing air access
to the primed filter, is central to the invention. Allowing air
access permits allows blocking air inclusions removed during
priming to re-form in the filter pore structure, significantly
reducing flow until the primed condition is re-established. The
advantage of maintaining the prime extends to essentially any
micro-porous filter medium regardless of composition, including
ceramic, carbon, or polymer membranes or filter bodies of inorganic
or organic composition.
An important aspect of the invention, therefore, is the use of a
filter cartridge design that keeps the filter media completely
submerged in water, so that air inclusions in the filter cannot
re-form. The use of such a design has been found very effective to
insure consistently high gravity flow rates for filter media of
sufficiently fine pore structure to provide parasite
filtration.
One specific embodiment of the invention, then, is a gravity-flow
water filter cartridge that includes a water-retaining reservoir
within which the micro-porous high-surface-area cyst reduction
filter element for the filter cartridge is disposed. The reservoir
has a retained water capacity sufficient to at least cover the cyst
reduction filter element when the cartridge is in an upright
orientation.
Preferably, the reservoir configuration is such as to retain a
quantity of water within the cartridge at a level at least
sufficient to cover the filter element, with coverage being
maintained over a range of cartridge tilt angles from upright (0
degrees) to at least 90 degrees from the upright orientation in at
least one tilting direction. For purposes of the present
description, upright orientation for a filter cartridge is the
filtering orientation in which the cartridge is held when mounted
for effective water filtration in a water carafe standing on its
base. This is a vertical orientation permitting water being
filtered to flow generally downwardly through the cartridge under
the force of gravity alone from a reservoir for raw water
positioned above the cartridge inlet to a treated water reservoir
positioned below it.
A particularly preferred embodiment of the filter design of the
invention is a gravity-flow filter cartridge comprising the
micro-porous filter in combination with other water-purifying
elements. Thus the cartridge will comprising a filter housing for
the various purifying elements, these elements comprising activated
carbon adsorbents, ion-exchange resins or compounds, and/or polymer
or ceramic filtering elements. The filter housing is adapted for
mounting in a vertical or filtering orientation within a holder for
the cartridge in a water carafe.
At least one of the filtration elements in the cartridge is a
micro-porous water filtration element having a pore structure
sufficiently fine to provide cyst reduction capability. To prevent
air blocking of this element, the filter housing incorporates means
for preventing air contact with the element while the filter
housing is in a tipped or pouring orientation, as well as while it
is in the filtering orientation. In general, such means operate to
retain a sufficient reservoir of water around the micro-porous
filter element that the element remains immersed in water under all
of the ordinarily encountered orientations assumed by the filter
housing during filling, pouring, and other normal uses of the
carafe.
In addition to rapid and effective parasite reduction, provided by
the primed micro-porous filter element, the preferred filter
cartridges of the invention have the capability to remove a variety
of other impurities from raw water. Thus these cartridges typically
include additional water-purifying elements such as resins, carbon
or silicate adsorbents, and coarse filters. Any of these
conventional elements may be included in the cartridge for the
removal of inorganic particulates, tastes and odors arising from
organic or inorganic impurities, organic solvent fractions or
pesticide residues, and ionic impurities such as lead and iron.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention may be further understood by reference to the
drawings, wherein:
FIGS. 1a-1d are schematic elevational views of basic cartridge
designs according to the invention;
FIGS. 2a-2c are schematic elevational views of some additional
cartridge designs;
FIG. 3 is an exploded perspective view of a preferred water up-flow
cartridge design;
FIG. 4 is a schematic view of a cartridge-carafe combination
incorporating means for restricting air access to filter elements
in the cartridge; and
FIG. 5 is a schematic view of a further cartridge-carafe
combination for restricting air access.
DETAILED DESCRIPTION
In a preferred embodiment, the filter cartridge of the invention is
composed of four constituents. These may be provided separately, or
in some cases combined in the same element. They include: (a) an
ion exchange medium (to remove lead and soften water); (b)
activated carbon (to remove tastes and odors and, if present in
sufficient quantities, organic chemicals); (c) a high-surface-area
micro-porous filter element for parasite (cyst) reduction; and (d)
a filter housing incorporating means for retaining water around the
filter element during normal cartridge use. Optionally, the
cartridge may include a pre-filter located in front of (upstream
from) the micro-porous filter element with respect to the direction
of water flow. This pre-filter can serve to prevent clogging of the
micro-porous filter element in cases where the raw water contains
significant concentrations of visible particulates.
The first two constituents, i.e., ion exchange media and activated
carbon, may if desired be included in the form of conventional
powders, beads or granules of the types used in prior art water
carafe filter cartridges. These are commercially available.
The third constituent of the cartridge is a high-surface-area
micro-porous filter element. This element may be formed of any of a
variety of different materials that offer porosity sufficiently
fine to provide effective cyst reduction. The structure must,
however, offer high surface area in order that adequate water
filtration rates under gravity force alone are secured. Examples of
materials that can be formed into filter elements of the requisite
porosity and surface area are porous ceramics, porous carbon,
composite materials of organic/organic, organic/inorganic or
inorganic/inorganic composition, and polymer or molecular sieve
membranes.
Among the various useful filter types are certain carbon-containing
porous ceramic honeycomb structures, made as generally described in
U.S. Pat. No. 5,597,617 and suitably plugged to provide
high-surface-area wall-flow filters as generally described in
published European Patent application EP 0754416. The co-pending,
commonly assigned U.S. provisional patent application of W. Cutler
et al., Ser. No. 60/068124 filed Dec. 19, 1997 now pending as
patent application Ser. No. 09/211,134 filed on Dec. 14, 1998,
describes certain porous high-surface-area ceramic filter elements
useful for cyst reduction in water carafe or other gravity flow
systems, and that application is expressly incorporated herein by
reference for a further description of this particular type of
filter.
Since maintaining the micro-porous filter element in a primed
condition is critical to the invention, the design of the filter
housing is of particular importance. It is in fact the filter
housing which enables the other elements, particularly the high
surface area filter element, to be effectively used in a gravity
flow water filtration environment.
The preferred practice of the invention involves placing the
purification elements of filter cartridge into the cartridge
housing, and then permanently priming the high-surface-area
micro-porous filter element to replace air from the pores of the
filter with water. The high surface area media is from then on kept
completely submerged in water (not just kept moist or wet)
throughout the period of normal use. Since normal use comprises
carafe filling, filtering and pouring, the means provided for
maintaining filter immersion must be operable over a range of
cartridge orientation angles. These range from upright or vertical
orientation (i.e., the orientation of the cartridge when mounted in
a carafe sitting on its base) to the tilted orientation assumed by
the cartridge when the carafe is pouring. This will typically
involve a cartridge tilt angle of at least 90.degree.; more
preferable is a cartridge design that maintains filter immersion
from the vertical through a tilt angle of at least 150.degree. in
at least one tilt direction.
In some cases, as where priming of the cartridge is carried out as
part of the manufacturing process, the cartridge will be shipped
and stored in a pre-primed condition. Since in these cases the
cartridge may assume any orientation, the cartridge will typically
be provided with temporary seals applied to the inlet and outlet
ports to prevent air access to the micro-porous filter element.
The path of water flow through the cartridge is not critical to the
invention. The flow path may be convoluted or direct, and include
flow-path segments directed upwardly (against gravity), laterally,
downwardly, or in various combinations thereof. Further, the
cartridge housing may, in addition to raw water inlet and treated
water outlet openings, include such features as a main filtration
chamber, various water transfer passages, air vents, water valves
and/or tubing. These will be designed to control water flow within
the cartridge and, most importantly, to prevent exposure of the
micro-porous filtration medium to air in both the upright and
tilted cartridge orientations.
FIGS. 1a-1d present schematic elevational cross-section views of
four differently designed filter cartridges, illustrating some of
the various water flow patterns useful in gravity flow cartridges
provided according to the invention. In FIG. 1a, water enters
filter cartridge 10a via gravity flow in the direction of arrow 8
through a vented top surface in cartridge housing 14. It then flows
downwardly through an ion-exchange bed 16 and a micro-porous filter
element 18 located in the main chamber of housing 14 before
entering an outlet conduit 20 formed within the cartridge. Conduit
20 is a trap outlet conduit of "gooseneck" configuration, and it
provides an overflow discharge path for the release of filtered
water from the cartridge. The configuration of conduit 20 insures
that, during and after filtration, the level of water within
housing 14 will be maintained at the height of sill 20a. Thus
micro-porous filter element 18 will be maintained in a submerged
and primed condition even after the flow of water through the
cartridge ceases.
In FIG. 1b, raw water enters cartridge 10b in the direction of
arrow 8 through inlet conduit 21, then entering the base of housing
14 beneath micro-porous filter element 18. It then flows upwardly
through filter element 18 and ion-exchange bed 16 to exit the main
chamber of housing 14 via overflow discharge conduit 22. The height
of sill 22a in discharge conduit 22 insures that the main chamber
of housing 14 will remain full and filter element 18 submerged.
FIG. 1c illustrates a cartridge design that combines both upward
and downward water flows in a single housing. Raw water initially
enters housing 14 of cartridge 10c by gravity flow through a top
vent in the housing, then filtering downwardly through ion exchange
bed 16. The ion-exchanged water then exits the upper portion of the
main housing chamber via by-pass conduit 23, entering the bottom of
the lower portion of housing 14 beneath micro-porous filter element
18. Under the pressure of the water head in the ion exchange bed
and conduit 23, water being filtered then flows upwardly through
filter element 18 and exits the cartridge housing via overflow
outlet conduit 24. Again, sill 24a in outlet conduit 24 insures
that water sufficient to keep filter element 18 submerged is
retained in the cartridge even after the flow of raw water from
conduit through the lower portion of housing 14 ceases.
In FIG. 1d, a baffle 44 is positioned within housing 14 of
cartridge 10 between filter element 18 and upstream water treating
elements such as ion-exchange bed 16. The baffle allows water flow
into the filter element section of the housing only through an
opening 46 located at a point in the baffle opposite the side of
the cartridge toward which tipping of the cartridge will occur in
use. To further improve priming protection at high tipping angles,
micro-porous filter element 18 is offset away from the baffle
opening toward the tipping side of the cartridge by inserting dead
space 40 in the filter chamber beneath the baffle opening. Draining
of the filter chamber is then prevented until a tilt angle
sufficient to raise at least some portion of the filter element
above the level of the baffle opening is reached.
The filter cartridges of the invention may additionally employ one
or more flow control valves at various locations within the
housing, to further reduce the likelihood of air access to the
micro-porous filter element in use. The valves may be simple
mechanisms such as float valves, check valves, or flapper valves,
or they may be manually operated valves actuated, for example, by
the user as pouring and tilting of the cartridge is initiated.
Again, just as in the case of the active cyst filter and other
purifying elements contained within the cartridge, the location of
the individual valve, conduit, or other flow control means within
the cartridge is not critical as long as the arrangement is such as
to preserve the prime of the micro-porous cyst reduction element in
use.
Examples of specific element arrangements and valves useful in
conjunction with filter cartridges provided in accordance with the
invention are illustrated in schematic elevational cross-section in
FIGS. 2a-2c. Filter cartridge 10d shown in FIG. 2a has an
arrangement of components similar to the arrangement of the
cartridges in FIGS. 1a-1c, except that water entering the cartridge
through a top vent in housing 14 flows through check valve 12
before entering the main filtering chamber of the cartridge. Check
valve 12 operates to prevent draining of the main chamber
containing cyst filter 18 when the filter cartridge is tipped with
a carafe containing it during pouring. Thus, in both filtering and
pouring orientations of the cartridge, a reservoir of water is
maintained in main chamber by the combined action of overflow
conduit 20 and check valve 12 which effectively prevents air access
to the filter element in use.
The design of the filter cartridge of FIG. 2b is similar to that of
FIG. 2a, except that the location of check valve 12 in cartridge
10e has been moved to a point between ion-exchange bed 16 and
micro-porous filter element 18. Again however, sill 20a in trap
outlet 20 is of a height such that water sufficient to cover filter
element 18 is retained in the bottom portion of the housing while
the cartridge is in a vertical or filtering orientation. Thus check
valve 12 is effective to prevent emptying of the critical bottom
portion of housing 14 when the cartridge is tipped for pouring.
In the design of filter cartridge 10f in FIG. 2c, check valve 12
has been moved to a point within trap outlet 20. The function of
the check valve in this design is to maintain the trap outlet in a
filled condition so that air does not have to be expelled from the
outlet during each fill cycle. The placement of the check valves
shown in the cartridge designs of FIGS. 2a-2c is generally
effective to keep filter element 18 submerged at cartridge pouring
or tilting angles of 90 degrees and in some cases up to 150 degrees
or more, at least in tilting directions away from the side of the
cartridge housing incorporating the discharge conduits. Of course,
where tilting to more extreme angles or in other directions is
anticipated, additional check valves or other water retaining means
may be included in the design.
In any of the cartridge designs of FIGS. 2a-2c or 1a-1d, the
discharge conduits may be vented to reduce siphoning effects which
might otherwise tend to draw water from the housing. For example,
FIG. 2a shows an optional vent 20c, which may be used to increase
the resistance of conduit 20 to siphoning. Air vents of similar
type can also be used in other locations within the cartridge as
necessary to relieve air buildup.
An example of the use of a manually operated valve to protect the
cartridge from air ingress in use in a water carafe would be a
manual plunger connected to the cartridge adjacent the cartridge
raw water inlet. This plunger would close the cartridge inlet
during pouring from the carafe, preventing the release of water
from the inlet and thereby avoiding the introduction of an air
bubble which could lead to a loss of prime in the porous
micro-filter. A button or other control means positioned on the
handle of the carafe incorporating the filter, having the primary
function of opening the carafe pour spout to dispense filtered
water, could secondarily activate such a plunger.
As previously noted, the performance advantages of filter
cartridges provided in accordance with the invention are not
limited to micro-porous filter elements of any particular class. In
fact, advantages may be seen even in the case of micro-porous
polymer membrane filter types which until recently have been used
mainly only in pressurized or "in-line" cyst reduction filtration
systems. Among the micro-porous filters known to be effective for
cyst reduction during water filtration are ceramic honeycomb
filters, carbon-based honeycomb filters, fiber mat filters
incorporating glass, ceramic and/or polymer fibers, and polymer
membrane filters. For purposes of the present description, the
designation of "cyst reduction filter" is limited to filters
providing .gtoreq.99.95% particle removal in standardized cyst
reduction tests.
The high gravity-only flow rate potential of many filter types
certified for cyst reduction has not previously been recognized,
since their use has been largely limited to high-pressure
filtration systems, and they have not been deployed in
high-surface-area configurations such as those of EP 0745416. Also,
the importance of excluding intermittent air contact with the
filter, which is normal in gravity flow systems, has not been
recognized.
We have found that such filters can exhibit surprisingly high
initial gravity flow rates if first adequately primed to remove air
from the fine pore structures of the filters. Further, when used in
the cartridge designs of the invention, gravity flow rates
exceeding 95% of the original primed flow are retained by these
types of filters over prolonged periods of use even though the
carafe reservoir is continually being filled and emptied. The
importance of prime maintenance in such cyst filters is illustrated
by the fact that these same filter types can show flow rates as low
as 1-20% of initial primed flow rates, if air access to the filter
elements between carafe fillings is permitted. Hydrophobic (e.g.
carbon or organic) cyst reduction materials are particularly
susceptible to this type of damage.
A particular example of a filter cartridge design incorporating
several of the above features is illustrated in the partially
exploded perspective view of FIG. 3. As illustrated in FIG. 3,
filter cartridge 10 is shown adjacent a cartridge mounting port 30
within which it will be mounted in actual use, port 30 providing an
opening in the bottom of a raw water reservoir 32 (shown in partial
cutaway view). Cartridge 10 comprises a base housing 14 and a main
cover 15. Cover 15 is shown separate from the housing to illustrate
the position of cyst reduction filter element 18 mounted in the
housing. The diameter of main cover 15 is slightly larger than that
of housing 14, being adapted to sealingly engage the top edge of
base housing 14 as the filter, cover and housing are assembled and
sealed during cartridge manufacture.
Cover 15 is fitted with a locking tab adapted to engage with a
locking groove in mounting port 30 within reservoir 32. Lock
mounting of the cartridge within reservoir 32 is desirable to seal
the mounted assembly against raw water leakage past the cartridge
in use.
To direct the flow of water through the cartridge, cover 15 is
provided with three small water flow ports 33-35, these being
positioned so as to establish the mode of operation of the
cartridge as an up-flow filter. In use, raw water from reservoir 32
first enters the cartridge through inlet port 33 in cap 15. This
water initially bypasses filter element 18, flowing downwardly
through by-pass conduit 20d to exit the conduit through a side
outlet in the conduit (not shown) opening into the bottom section
of the main chamber of housing 14.
Due to the head pressure of the raw water in reservoir 32, raw
water entering the base of housing 14 flows upwardly through the
housing 14, eventually passing through filter element 18 for final
filtration. It then exits the main chamber of the housing 14 via
overflow port 34.
Covering ports 34 and 35 is a small flow connector 36, shown in
phantom above cap 15 in the exploded view of FIG. 3. When sealed to
cap 15 over ports 34 and 35 during cartridge manufacture, connector
36 functions as an elbow fitting to direct filtered water flowing
upwardly through overflow port 34 into drain port 35. In the
assembled cartridge, port 35 opens directly into drain conduit 20e,
the latter providing a drain through which the filtered water
empties from the cartridge into a filtered water reservoir of
conventional design (not shown) placed beneath reservoir 32 for
pure water collection. A screening cap 37, adapted to cover both
connector 36 and inlet port 33 in the fully assembled cartridge,
includes a screened inlet 37a which operates to remove large
particulates from the raw water stream before it enters the
cartridge.
One particular advantage of the cartridge assembly shown in FIG. 3,
in addition to its compact design, is good resistance to air
ingress at cartridge tipping angles greater than 90.degree. from
the vertical. The cap/water conduit combination shown is very
effective in trapping water within housing 14 during tilting of the
cartridge, thereby preventing air from infiltrating back into the
filter. Best results are achieved when, as the cartridge is locked
in position in a carafe, the conduit, ports, and cap fittings are
located nearest the side of the cartridge diametrically opposite
the side toward which cartridge tilting will occur during pouring
from the carafe.
Other methods for mitigating the effects of air ingress are shown
in FIGS. 4 and 5. In FIG. 4, an air chamber 40 is provided outside
of cartridge housing 14. As the cartridge is tipped during pouring,
any air bubble trapped above filter element 18 in the housing rises
into the chamber and is replaced by overflow water from the
chamber. In FIG. 5, a filter cartridge 10 positioned near the pour
spout of a carafe 44 in which it is mounted is fitted with an
extended raw water intake tube 42 terminating at a point spaced
from the cartridge inlet, and well above the inlet in the tipped or
water-dispensing cartridge orientation. The tube prevents water
drainage from the cartridge inlet, thereby avoiding the
introduction of air bubbles into the cartridge.
The cartridge designs specifically described and illustrated above
are intended to be merely illustrative of designs and methods for
successfully employing cyst reduction materials in gravity flow
filtration systems for the purification of drinking water. Various
adaptations of these designs and methods may therefore be resorted
to for the same or similar purposes within the scope of the
appended claims.
* * * * *